In the conventional receiver, each band group needs a dedicated mixer and operates independently. To decrease the chip area, some mixer sharing techniques are provided. In a first example, two band groups are coupled to an input terminal of the mixer via switches, respectively, and only one of the band groups is allowed to connect to the input terminal of the mixer at the same time. However, the switches of the first example provide additional parasitic load, and the input terminal of the mixer will see the parasitic load of two switches. In a second example, two band groups are directly connected to the input terminal of the mixer, and only one of the band groups is enabled to transmit a signal to the input terminal of the mixer at the same time. However, the load of the band groups needs to be co-designed, and the input terminal of the mixer will see the parasitic load of two band groups, causing a worse performance of the receiver.